Re: Qemu/nvmm - time in NetBSD guest system lags behind (with estd on host)

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Sat, 3 Sep 2022 13:51:25 +0200
    From:        Matthias Petermann <mp%petermann-it.de@localhost>
    Message-ID:  <8c9bbdbc-5583-7f2d-4e04-ab550b6eeb6e%petermann-it.de@localhost>

I cannot really help with zfs issues, I know nothing about it, but:

  | The zfs module was loaded though, I also built the kernel with exactly
  | the same sources as the "original" one, so I assume for now that the
  | modules are compatible.

if that implies that you rebuilt the kernel with HZ=1000 and then used
the zfs module built with HZ=100 then I think the first thing I would try
would be to rebuild the module(s?) with HZ=1000

Long ago there was much work done to get rid of the constant HZ from the
kernel, and replace it with the variable hz (which is initialised to HZ).

However, I am by no means sure that this has consistently been maintained
in all the intervening years, and in particular with external modules, and
there might be places that are still (or again) using HZ (the constant)
rather than hz (the variable) (but beware just doing a grep, in many contexts
there is a #define HZ hz in scope that can defeat that simple way of checking).

While you definitely need new modules if the kernel version changes, I
don't believe that the converse applies.   I suspect you need new modules
(or might) when kernel options change as well (whether you do or not
depends upon whether the module is affected by the option that has been
changed - which is not always easy to detect, so just rebuilding is
generally safer.)

kre